Generally, a wind turbine includes a tower, a nacelle mounted on the tower, and a rotor coupled to the nacelle. The rotor typically includes a rotatable hub and a plurality of rotor blades coupled to and extending outwardly from the hub. Each rotor blade may be spaced about the hub so as to facilitate rotating the rotor to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy.
The tower typically includes a base section and an upper section. The base section of the tower is secured to a foundation. The foundation may be a concrete slab (raft) foundation, a short pole type foundation, a deep piling foundation, or any other suitable foundation capable of supporting loads produced by wind, turbine operation, and gravitational forces with usage of an anchor cage. A typical interface between the tower base portion and an anchor cage foundation has a bottom T-flange attached to a tower base adapter or a door section.
Due to high transportation and manufacturing costs, however, the tower base adapter and the door section are becoming prohibitively expensive. For example, the bottom T-flanges must be welded to the tower base adapter and/or the door section, which requires welding certification. Weld fatigue is a critical factor contributing to increased manufacturing costs. Further, the T-flange of the tower base adapter or the door section increases transportation costs because it exceeds the transportation size limits and restricts available routes. Additionally, the tower base adapter increases manufacturing costs due to the extra pair of L-flanges required to secure the tower base adapter to the base section of the tower.
By eliminating the tower base adapter and the door section, thereby eliminating the requirement of the welded T-flange, the tower outer diameter can be maximized to the transportation limit. Further, eliminating the tower base adapter or the door section allows the tower entry door to be located at a lower height above the foundation, saving costs associated with external stairs and structures. Additionally, the space inside the tower, where the extra pair of L-flanges from the tower base adapter is normally located, would be increased by removing the tower base adapter, thereby allowing easier access to maintenance and electrical equipment.
Accordingly, a wind turbine with an improved interface between the base section of the tower and the foundation would be desired in the art. For example, replacing the tower base adapter or door section T-flange with a detachable tower base ring assembly would be advantageous. The present invention, therefore, discloses a detachable tower base ring assembly that secures the L-flange of the base section of the tower to a foundation, which eliminates the need for a welded T-flange and an extra set of L-flanges of the tower.